Error on calling Method with Authorize-Attribut

[volkhardv]

Hello,
i was trying this sample with Keycloak Version 19.0.1 with changing the Authoriy-Url to http://keycloakserver/auth/realms/test

When calliung an Authorize-protected WebService with an new token i get the following error-message:
System.InvalidOperationException: IDX20803: Unable to obtain configuration from: 'System.String'.
---> System.IO.IOException: IDX20807: Unable to retrieve document from: 'System.String'. HttpResponseMessage: 'System.Net.Http.HttpResponseMessage', HttpResponseMessage.Content: 'System.String'.
at Microsoft.IdentityModel.Protocols.HttpDocumentRetriever.GetDocumentAsync(String address, CancellationToken cancel)
at Microsoft.IdentityModel.Protocols.OpenIdConnect.OpenIdConnectConfigurationRetriever.GetAsync(String address, IDocumentRetriever retriever, CancellationToken cancel)
at Microsoft.IdentityModel.Protocols.ConfigurationManager1.GetConfigurationAsync(CancellationToken cancel) --- End of inner exception stack trace --- at Microsoft.IdentityModel.Protocols.ConfigurationManager1.GetConfigurationAsync(CancellationToken cancel)
at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.HandleAuthenticateAsync()
at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.HandleAuthenticateAsync()
at Microsoft.AspNetCore.Authentication.AuthenticationHandler`1.AuthenticateAsync()
at Microsoft.AspNetCore.Authentication.AuthenticationService.AuthenticateAsync(HttpContext context, String scheme)
at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

do you have an idea?

best regards

Volkhard